Q.: Through an error, 1 percent calcium chloride was added to a 3000-psi concrete mix which was used for a slab over a galvanized metal deck. The specification clearly prohibits the use of the admixture. The structural engineer and the architect have directed us to either remove the slab or show that there will be no detrimental effects from the addition of the calcium chloride. The removal would cause unacceptable delays to completion and occupancy. Is the calcium chloride detrimental to the concrete or the deck?
A.: The chloride will have no detrimental effect on the concrete itself but it is likely that the concrete would eventually corrode the metal deck. In the article "The Role of Calcium Chloride in Concrete," Concrete Construction, February 1976, page 57, Bernard Erlin and William G. Hime cite six case histories of corrosion from calcium chloride. In one case interior steel door jambs were inset in concrete containing 1.4 percent calcium chloride dihydrate by weight of cement. Within 1 year after construction the steel jambs were eaten through in many areas and moderately corroded in others.